Insulin and glucose tolerance assessment in guanylyl cyclase/natriuretic peptide receptor-A gene-targeted mutant mice

Abstract

Atrial natriuretic peptide (ANP), acting through guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) regulates blood pressure and cardiac homeostasis. The disruption of Npr1 (encoding NPRA) in mice exhibits hypertension and provokes renal and cardiac disorder. However, the underlying mechanisms are not yet precisely determined. The objective of this study was to determine whether Npr1 plays a role in regulating glucose homeostasis in global Npr1 gene-disrupted mice. The adult male (14-18 wks) Npr1 haplotype gene-knockout ( Npr1+/-, 1-copy), wild-type ( Npr1+/+, 2-copy), and gene-duplicated ( Npr1+ +/+ +, 4-copy) mice were fasted overnight (16 h) and given free access to water. The mice were administered with glucose both orally and intraperitoneally (2 g/kg body weight) to determine the oral glucose tolerance test (OGTT) and intraperitoneal glucose tolerance test (IPGTT). For the insulin tolerance test (ITT), mice were also fasted for 16 h and then received an ip-injection of insulin (1.0 UI/kg body weight). Blood glucose levels were determined by performing tail bleeds at 0, 15, 30, 60, 90, and 120 min using the AlphaTRAK blood glucose monitoring system. The results showed that administration of glucose resulted in a greater increases in blood glucose levels at 120 mins in 1-copy mice (OGTT: 237 ± 5 mg/dL, IPGT: 246 ± 6 mg/dL, ITT; 239 ± 7 mg/dL) than 2-copy male (OGTT: 131 ± 3 mg/dL, IPGT: 126 ± 6 mg/dL, ITT; 127 ± 6 mg/dL), respectively. The blood glucose was also significantly lower in 4-copy mice (OGTT: 113 ± 5 mg/dL, IPGT: 108 ± 7 mg/dL, ITT; 107 ± 3 mg/dL) than in 2-copy mice. Systolic blood pressure (SBP) was determined by non-invasive tail-cuff method (Visitech 2000). SBP was significantly greater in 1-copy mice (130 ± 4 mmHg) than 2-copy mice (100 ± 3 mmHg). Similarly, SBP was also significantly lower in 4-copy mice (90 ± 2) than 2-copy mice. The increase in plasma glucose levels was significantly lower in OGTT than in IPGTT. The present results suggest that decreased Npr1 gene copy number predisposes to hyperglycemia, insulin resistance, and hypertension. These results indicate that the Npr1 gene might regulate blood glucose homeostasis. This work was supported by the NIH grant (DK133833). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.